1. Field of the Invention
A microscopic spectrometer capable of irradiating a sample with light and then the light reflected by or through the sample is spectrometrically measured and, more particularly, a microscopic spectrometer having an auxiliary imaging system for targeting a portion of the sample is provided.
2. Description of Related Art
Microscopic spectrometers have proved to be a valuable tool in determining the properties of samples irradiated with light. Referring to FIG. 3, a conventional microscopic spectrometer arrangement is disclosed. A sample 2 is irradiated with light from a light source 1, and the light, which has transmitted through the sample, is subsequently collected by an object lens 3, which is shown in a schematic form, to provide an enlarged image on an image surface 4. This image is focused through a relay lens 5, shown in a schematic form, so that it can be observed by means of an eye piece 6, also shown in schematic form. When it is desired to provide a spectrometric measurement, an optical path changing mirror is positioned between the image surface 4 and the relay lens 5 to reflect the light to a spectrometric measurement system 8. This system is capable of measuring a spectrum of transmitted light in a known manner and a display device can provide the output of this analysis.
It is frequently necessary to measure the spectrum of merely a portion A of the total sample 2, as shown in, for example, FIG. 4(a). As can be seen, however, the entire sample 2 is realized as an image of the object to be measured so that a mixture spectrum of the substances A, B, and C would be obtained. In order to solve this problem, the image surface 4 is provided with relatively movable masks 10 and 11, as shown, respectively, in FIGS. 3 and 4(b). One set of masks is moved in the X plane, while another set of masks can be moved in the Y plane to enable a rectangular slit or a square to be realized while shading beams of illumination from the specimen from the other areas of the target object. Generally, the respective masks 10 and 11, or shutters 10 and 11, are formed in the shape of a knife edge with their lens optionally changeable to shade, for example, light from substances B and C other than desired substance A, whereby the substance A can be measured with an appropriate adjustment of the slit length so that only light beams from the substance A will be received, as shown in FIGS. 4(b) and 4(c). While such a procedure is effective in providing the desired spectrum of light to be analyzed, it creates a significant problem in the conventional microscopic spectrometer, because the use of the masks also limits the field which can be observed through the masks 10 and 11, as shown in FIG. 4(c). Since the other substances B and C of the specimen are shaded or blocked from view, any positional relationship of the substance A to the entire image of the sample 2 cannot be observed. Additionally, the positional relationship of the object to be measured through the masks 10 and 11 will be considerably reduced. As can be appreciated, it is frequently necessary to understand the relationship of the measured portion relative to the entire image of the substance to be measured, such as, for example, in measuring a semiconductor chip, or the cellular tissue of a living body. As a result, it is frequently necessary for the technician to reconfigure the positional relationship of the object to be measured by moving the masks 10 and 11 or by enlarging or moving the slit between the masks. This creates an additional problem in that any secondary measurements to reconfirm an initial measurement will become extremely difficult, since the reproduced positions of the masks 10 and 11 and the exact slit length parameter and its relationship to the sample will be extremely difficult to reproduce, thereby reducing the accuracy and the confidence in the measurement procedure.
Thus, in the prior art there is still a demand to improve a microscopic spectrometer to ensure both the accuracy and ease of operation of the instrument.